AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil
AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil (AME) is a 100% synthetic, dual-purpose SAE 15W-40 lubricant for pre-emissions on-road and off-road diesels, marine diesel inboards, and severe-service equipment that runs without exhaust aftertreatment. The formula carries a Total Base Number of 12.1 to neutralize acids and control soot thickening from EGR and blow-by, with a heavy-duty dispersant/detergent additive package built for long hours, sooty cycles, and high temperatures.
High TBN soot and acid control
The 12.1 Total Base Number gives AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil a deep alkaline reserve that neutralizes combustion acids and the sulfur-derived acids found in low- and high-sulfur diesel fuels. The dispersant/detergent system suspends soot particles independently so they cannot agglomerate into the larger, abrasive clusters that drive cylinder bore polishing, ring wear, and oil thickening in EGR-equipped engines. Four-Ball Wear Test results show a 0.48 mm average scar (ASTM D4172).
Cold-flow properties for marine and winter starts
Pour point is rated at -38 degrees C (-36 degrees F) with a CCS viscosity of 5173 cP at -20 degrees C (ASTM D5293). The synthetic base oils flow into the pump pickup and up to top-end components quickly on cold cranks, which matters for unheated marine engine rooms in spring commissioning, off-road equipment in northern climates, and over-the-road trucks idling outside through winter shifts.
Low volatility for reduced consumption and emissions
Noack volatility measures 4.2 percent weight loss (ASTM D5800), well below typical mineral 15W-40 diesel oils. Less light-end vapor passes the rings into the combustion chamber, so makeup-oil intervals stretch out and exhaust-side oil-burn deposits stay lower. The film also holds its rated viscosity through high-temperature service, which protects bearings and turbo journals during extended high-load runs.
Shear-stable viscosity for turbo and high-load duty
Kinematic viscosity is 15.4 cSt at 100 degrees C and 112.9 cSt at 40 degrees C (ASTM D445), viscosity index 143 (ASTM D2270), and high-temperature/high-shear viscosity 4.3 cP (ASTM D5481). The HTHS reading sits above the 3.7 cP minimum required for SAE xW-40 grades, which preserves the hydrodynamic film at peak crankshaft and turbo bearing loads.
OEM and industry approvals for legacy diesels
AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil meets API CI-4+, CI-4, CH-4, CF, CF-2, SL, and SJ. It also covers ACEA A3/B3, E2, E3, E5, E7, Global DHD-1, and JASO DH-1, plus Caterpillar ECF-1A and ECF-2, Cummins CES 20076, 20077, and 20078, Mack EO-M and EO-N, DDC 93K214, Volvo VDS-2 and VDS-3, MB 228.1, 228.3, and 229.1, MAN 271 and 3275, and MTU Type II. This is the older heavy-duty diesel category, intended for engines built before DPF and SCR aftertreatment, including pre-2007 over-the-road trucks, naturally aspirated and turbocharged marine inboards, and stationary industrial diesels.
Marine inboard suitability
The marine side targets diesel inboards and sterndrives that share the pre-aftertreatment heavy-duty diesel category above, which covers many older Cummins MerCruiser Diesel, Volvo Penta diesel, Yanmar diesel inboard, Caterpillar marine diesel, and Detroit Diesel marine applications. Gasoline marine outboards and four-stroke sterndrives use different TC-W3 or NMMA FC-W product families.
Recommended applications and service intervals
AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil is engineered for light- and heavy-duty diesel engines without exhaust aftertreatment, including over-the-road trucks, off-road construction, marine diesel inboards, farm equipment, mining, industrial pumps and generators, and personal or commercial transportation. It works in standard, turbocharged, and supercharged diesels (including EGR systems) on low- or high-sulfur diesel fuel, and in gasoline engines that call for the listed API S-series categories.
- Use the current AMSOIL product page, the engine manual, and oil-analysis results to set the service interval.
- Extended service depends on engine type, operating conditions, filtration, fuel, and maintenance history.
- Severe and normal service definitions follow OEM guidance.
- Not for use with engines equipped with exhaust aftertreatment systems, including DPF and SCR. Extended drains are not recommended on biofuels containing more than 10 percent ethanol or B10 biodiesel.
The formula is compatible with conventional and synthetic motor oils, but mixing shortens service life and voids the extended drain intervals. Aftermarket oil additives are not recommended. For a current API CK-4 platform that fits modern aftertreatment hardware, see AMSOIL Signature Series Max-Duty 15W-40 Synthetic Diesel Oil. Pair the fill with a high-efficiency full-flow filter sized to the engine, or add a bypass filtration system on long-haul and marine platforms to stretch service life further.
Typical technical properties
| Property | Value |
|---|
| Kinematic Viscosity at 100 degrees C, cSt (ASTM D445) | 15.4 |
| Kinematic Viscosity at 40 degrees C, cSt (ASTM D445) | 112.9 |
| Viscosity Index (ASTM D2270) | 143 |
| CCS Viscosity at -20 degrees C, cP (ASTM D5293) | 5173 |
| Pour Point, degrees C (degrees F) (ASTM D97) | -38 (-36) |
| Four-Ball Wear Test (ASTM D4172), Scar, mm | 0.48 |
| Noack Volatility, percent weight loss (ASTM D5800) | 4.2 |
| High-Temperature/High-Shear Viscosity (ASTM D5481), cP | 4.3 |
| Total Base Number | 12.1 |
Order AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil
Available sizes include the AMEQT quart bottle (each or case of 12), the AME1G one-gallon jug, the AMETP 2.5-gallon jug, the AME55 55-gallon drum, and the AME27 275-gallon tote, all backed by the AMSOIL Limited Warranty. Match the right viscosity, OEM specification, and emissions hardware to the application using the AMSOIL vehicle lookup guide and the AMSOIL diesel oil guide, then place the order through the Buy online link to the AME product listing.
Customer reviews
The best oil for old diesels
The 15w-40 heavy duty diesel and marine oil is the only oil I’d use in my old Dodge Cummins 24 valve with a flat tappet valve train. The newer CK-4 rates diesel engine oils are designed for the newer emissions engines with a DPF and roller valve trains. The CK-4 oils don’t have the additive package needed to protect the older diesels because those very lubrication & detergent additives, zinc, phosphorus, & calcium, will damage the DPF and emissions equipment on newer diesels. Oil manufacturers will say the newer CK-4 and higher oils are backwards compatible, but they truly aren’t. This is coming from a guy that has an AA degree in diesel mechanics, 37 years working for a heavy equipment dealership, 17 years as a HD mechanic, 3 years as a T/C which also involved managing the oil lab, and the last 17 as a product support rep. I truly hope Amsoil continues to keep the HD 15w-40 diesel & marine oil in their line up.
By Mike78 from Dixon, CA on June 01, 2026.
Would recommend this to a friend.
Has the correct API rating compared to other oil
My last conversation with one of your reps. Im so pleased to hear that your corporation has a location now in Dubai and Iran. Hopefully not Israel.
By Habeeb from AZ on February 27, 2026.
Would recommend this to a friend.
The best diesel oil for pre-emissions vehicles.
Got turned into this oil by a master mechanic for Detroit Marine Diesel engines. I have never used anything else in my duramax and recommend it to anyone that doesn’t have a DPF. I use oil analysis and the results wish for themselves.
By Hunter on November 12, 2025.
Would recommend this to a friend.
Read all 279 reviews
Frequently asked questions
Is 15W-40 diesel oil the same as marine diesel oil?
For inboard marine diesels, the same SAE 15W-40 heavy-duty diesel oil is normally specified, and AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil covers both duties. The marine label in the product name reflects suitability for diesel inboards in the same API CI-4+ and earlier categories. Gasoline marine outboards and four-stroke gasoline sterndrives use different NMMA FC-W or TC-W3 oils.
Can AMSOIL AME run in DPF or SCR equipped diesels?
No. AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil is not for use with engines equipped with exhaust aftertreatment systems, including diesel particulate filters and selective catalytic reduction systems. Modern emissions diesels need a low-SAPS API CK-4 or FA-4 oil such as AMSOIL Signature Series Max-Duty 15W-40 Synthetic Diesel Oil.
What engine oil should the owner use in a marine diesel inboard?
Match the manufacturer-required SAE viscosity grade and service category from the engine handbook, then confirm the current AMSOIL product-page guidance before service.
How often should the oil and filter be changed?
Use the current AMSOIL product page, the engine manual, and oil-analysis results to set the service interval. Extended service depends on engine type, operating conditions, filtration, fuel, and maintenance history.
Does AMSOIL AME cause oil leaks in older diesels?
The synthetic base oils and additive package are seal-compatible with the elastomers used across the API CI-4+ and earlier diesel categories. High-mileage engines with hardened or already-failing rear main, valve cover, or front cover seals can show leaks after any oil change because cleaner oil and reduced varnish loading reveal pre-existing seal damage. The fix is the seal, not the oil.
Is this the right oil for an older Cummins, Duramax LBZ, or 7.3L Power Stroke?
Pre-aftertreatment diesel pickups built through the 2007 model year (older Cummins, 7.3L and 6.0L Power Stroke, and Duramax LB7 and LBZ trucks without DPF) typically call for SAE 15W-40 in API CI-4+, CH-4, or earlier categories, which is the slot AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil fills. Trucks with a DPF need an API CK-4 oil such as AMSOIL Signature Series Max-Duty 15W-40 instead.
Can other oils be mixed with AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil?
Topping off with another conventional or synthetic motor oil is acceptable in an emergency, but extended drain intervals do not apply once the sump has been mixed. Aftermarket oil additives are not recommended because the AMSOIL formulation is already balanced for the rated service interval.
